The ALGOL 68 Project

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Introduction

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~kc4zvw: cat hello.alg
COMMENT
 ! Program: hello
 ! Author: David Billsbrough — E-mail
 !
COMMENT

printf(($gl$, "Hello World!"))

# End of File #
~kc4zvw:

  

Build Notes

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Parallel sieve of Erathostenes

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COMMENT

	This is a gratuitously parallel implementation of the sieve of Eratosthenes after
	a program contributed by Lawrence D’Oliveiro; the number of primes it can output is
	limited only by the number of threads 'a68g' can create.

COMMENT

PR heap=32M PR
PR frame=1M PR

MODE SIEVER = STRUCT (SEMA full, empty, REF INT n);
PROC make siever = SIEVER: (LEVEL 0, LEVEL 1, NEW INT);

PROC start siever = (SIEVER s, INT n) VOID:
	(n MOD 2 /= 0 | DOWN empty OF s; n OF s := n; UP full OF s);

PROC next unmarked = (SIEVER s) INT:
	(DOWN full OF s; INT n = n OF s; UP empty OF s; n);

PROC sieve = (SIEVER current) VOID:
	(INT n = next unmarked (current);
	print ((whole (n, -int width), new line));
	SIEVER new = make siever;
	PAR (
		DO IF INT i = next unmarked (current);
			i MOD n /= 0
			THEN start siever (new, i)
			FI
		OD,
		sieve (new)
	)
);

SIEVER first = make siever;
INT n := 1;

PAR (DO n PLUSAB 1; start siever (first, n) OD, sieve (first))

# EOF #
  

Summary

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Miscellaneous

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